In general terms, the main research conducted in this proposal is directed toward a better understanding of the action of narcotic analgesics and the development of tolerance and physical dependence to these drugs. More specifically the proposal concerns the following aspects. 1) Characterization of analgesic receptors 2) Transport of narcotics by the choroid plexus 3) Effect of narcotics on axonal transport 4) Effect of narcotics on amino acid transport into brain 5) Effect of diazepam on methadone metabolism and distribution 6) Calcium uptake by slices of various areas of the brain 7) Uptake and binding of 3H-etorphine and H3-naloxone by various parts of the brain 8) Characterization of morphine receptors in the guinea pig ileum.